Himalayan Griffon Vulture

This is my sixth vulture post in a row. The first four were found in Uganda in Africa and the last two were found in India in Asia. Four of them are listed as Critically Endangered by the IUCN. Today's subject, the Himalayan griffon vulture, also known as the Himalayan vulture and Himalayan griffon, is in much better shape than the others, it is listed as Near Threatened by the IUCN. 

I have posted a number of photos, below, of different vultures I saw in Kaziranga NP in Assam India in December 2024 on iNaturalist and none have received confirming responses from any identifiers. So today, I've deep dived on the subject, also looking at the slender-billed vulture I saw in Kaziranga, looked at other alternatives, and now I'm feeling more confident in some of the identifications. 

First is a bird that I feel pretty confident is a juvenile Himalayan griffon vulture. I was with my guide in the Eastern Range of Kaziranga and it was standing in a tree very near our vehicle. My guide, who was very knowledgeable about birds, identified it as a Himalayan griffon. Following are the four photos I have of it. 

Next is the illustration of the juvenile Himalayan griffon from Birds of the World which is what I believe the bird is. 

Next I give cropped photos from my first photo to focus on parts of the bird that I believe confirm it to be a juvenile Himalayan griffon. 

This first photo is cropped to give a larger view of the bird. 

This photo confirms it has a white head, blue around the eye and a whitish bill. The juvenile has a darker bill than the adult (I'll show the adult illustration later), but the adult's bill becomes whiter. I believe this juvenile's bill is transitioning from dark to whitish. It also has brownish tuft around the neck with some white. The juvenile has black tuft and the adult has whitish tuft. I believe that it is transitioning on this bird as well. The feathers on the illustration show lines going through them on the wings and thighs. This cropped photo below shows the feather shafts surrounded by white which corresponds with the illustration. 

Here is the illustration from Birds of the World which shows the adult Himalayan griffon. Note the whitish bill and the whitish tuft around its neck. 

The following photos were also taken in the Eastern Range of Kaziranga out in an open grass plain. I believe these are also transitioning Himalayan griffons from juvenile to adult. Note the white necks, the lines growing through the feathers and the tuft around the neck transitioning to white. Of course, these photos are not as clear as the photos for the first vulture. 

These next two vultures, also in the Eastern Range of Kaziranga NP are the hardest for me to identify. They are possibly the same bird, with photos taken at different times, as we were looking at a number of vultures in the same area. The head and neck look too dark to be Himalayan griffons, more consistent with a slender-billed, but they do have whitish elements to them. They have dark bills, which are consistent with a juvenile Himalayan or a slender-billed. The feathers don't seem to have the same lines through them as a Himalayan and perhaps more consistent with a slender-billed. It has a ruff around the neck which appears to be more consistent with a Himalayan. If someone reads this and has an idea, I'd love to get a response.